Neptune, the eighth planet of the Solar System, is built like a giant gas ball more than 17 times the size of Earth. It consists largely of hydrogen, helium and methane; since methane absorbs red light, the planet has a luminescent blue color.
Voyager 2 flew past Neptune in 1989 and discovered a great oval spot, similar to the one found on Jupiter. The cloud formation is about the size of earth. Voyager also discovered six new moons, in addition to the two that were known. It photographed a large, Grand Canyon-like fault on the surface of the moon of Triton.
Neptune was Voyager 2' s last encounter. In August of 1989, it left the Solar System to probe into the depths of interstellar space.
